Dark Problems

Chapter 5B

Dark Problems

AN EXAMPLE: THE DARK SIDE

It had been suspected for some time that galaxies had far more matter than we could determine from what was visible. Once we were able to look at galaxies in the full spectrum we realized that perhaps as much as 90% of some galaxies’ mass was unaccounted for (one main reason for this realization is that the outer stars in a galaxy are going so fast that without that much extra mass to keep them in, they would be flung into intergalactic space). But apparently most of that missing mass (now called “dark matter”) cannot be seen, for it does not interact with ordinary matter, except through gravity. In other words, most of the matter in the universe is completely different from anything we have known until now (it is not made up of protons, neutrons, electrons and the like). To study dark matter it is necessary to observe the universe with space telescopes, as will be explained below.

To make matters worse, it was discovered that the expansion of the universe is accelerating, in violation of the sensible belief that gravitational attraction should slow down and perhaps even reverse the expansion initiated in the most famous of all explosions, the Big Bang. A new form of energy, Dark Energy, which we understand even less than we understand Dark Matter, presumably accounts for that perplexing expansion. Since dark energy and dark matter take up most of the universe, our precious Standard Model tries to explain the entire universe on the basis of the less than ten percent of matter that it is acquainted with. Imagine that you come to a new place and get to know ten percent of it. All you know about the rest is that it is completely different from the small portion you know. How confident would you feel about explaining the whole on the basis of the one part you can handle? And then add the complication that Dark Energy make up two thirds of the universe!

Again, to study dark energy we need to go into space, sooner or later. Some of the work of surveying the universe can be done with terrestrial telescopes, but the findings of such surveys will have to be corroborated and supplemented by telescopes in orbit, as we will see below. This means that to have much of a chance to come up with a fundamental explanation of the universe we need to do space science. Some physicists still hope that in the new particle accelerators, which will produce very high energies, violent collisions will yield some dark matter particles. And, who knows, their hopes may perchance be realized, but since we do not know what dark matter is, those physicists sound a bit too optimistic. And even then we would still have the even bigger puzzle of dark energy.

To do away with the problem of Dark Energy, some physicists have proposed to replace the Theory of General Relativity with another theory in which gravity is not a constant. This hypothesis, which is rejected by most physicists, would of course represent a radical transformation of fundamental physics brought about by space astronomy and physics. Either way, space science should receive significant credit for the serendipity that will result from the soon-to-be new physics.

SPACE SCIENCE AND THE TRADITION OF FUNDAMENTAL PHYSICS

Let us begin our discussion of Claim (1) by remembering that the connection with astrophysics has been a trademark of modern physical science from its inception and throughout most of its history.

Although it is well known that Copernicus proposed that the sun and not the Earth was at the center of the universe, his motivation is not so well understood. It was not that his system could account for the position of the planets clearly better than the Ptolemaic system, for even Copernicus acknowledged that the matter was not settled. Nor was it obvious either, in spite of the claims by Pierre Duhem and others, that his system was vastly simpler. It is true that the Ptolemaic system employed a variety of mechanisms--epicycles, eccentrics, deferents, equants--to account for the paths of the planets, but with the exception of the equant so did the Copernican system. (See figures).[1] The difference was that the Ptolemaic system often had alternative combinations of such mechanisms for different aspects of the behavior of the same planet. This would seem outrageous to someone weaned on the notion that only one such mechanism could be correct. But the mere talk of correctness assumes that we can inquire about the real nature of the heavens.

We feel entitled to make that assumption rather freely today. But that was not the case in Copernicus' day. From the time of Ptolemy (second century AD.), the inquiry about the reality of the heavens had been looked upon with suspicion. The reason was that whereas the progress of mathematical astronomy made it possible to calculate with increasing precision the positions of the planets, the accounts of why the planets moved as they did had broken down not long after Aristotle had proposed the interaction of concentric spheres made of his quintessence (about 350 BC.).

According to Ptolemy himself, mathematics can apply only to "changes in form: i.e. in trajectory, shape, quantity, size, position, time, and the rest."[2] As to the actual nature of things there is little that science can do because they either take "place far above us, among the highest things in the universe, far away from the objects we directly observe with our senses," or else, as the objects of (terrestrial) physics, those "material things...are so unstable and difficult to fathom that one can never hope to get philosophers to agree about them."[3] Questions about the nature of the heavenly objects must lead one back to the ultimate source of all change, and thus they can only be answered by theology. Therefore science gains little to profit from asking them. And they are also distinct in kind from the sorts of questions that physics tries to answer, whose underlying principles, if any, did not seem amenable to mathematical treatment.

In the long run the Copernican revolution accomplished several important changes in points of view. For one thing it insisted in investigating the nature of the behavior of the heavenly objects. And it did so by looking for mutual underlying mathematical principles for both the heavens and the Earth. The success of this gross violation of Ptolemy's methodological rules turned on Copernicus' belief that astrophysics was possible. Eventually Newton succeeded where Aristotle had failed, and astrophysics became the shining example that new branches of physics had to follow.

Confusions about Copernicus' motivation were created mainly by Osiander's preface to Copernicus' masterpiece, On the Revolutions. Fearing a confrontation with theological dogma, Osiander urged the readers to "permit these new hypotheses to become known together with the ancient hypotheses," and to do so because Copernicus' hypotheses are "admirable and also simple, and bring with them a huge treasure of skillful observations." But the Copernicus' reader, Osiander wrote, should not accept as the truth "ideas conceived for another purpose."[4] All these admonitions by Osiander contradict Copernicus' own words and belie his attempt to discover the truth about the heavens by rational means instead of revelation.

In the centuries following Copernicus, astrophysics continued as a driving force of fundamental theory. Newton is, of course, the most prominent example. His laws of dynamics applied equally to terrestrial and heavenly objects, and his law of gravitation was a striking statement of the discovery that the force that kept us glued to the surface of the Earth was the same that made the stars and planets keep their appointed rounds.

We begin to see why this view of science is distorted when we realize that fundamental questions often cannot be asked without the appropriate technology and will not be asked without the right kind of inspiration and motivation. But this realization leads to another: that a whole host of activities are potentially as crucial to scientific progress as work that aims to solve problems within the most prestigious field of the time. Researchers who create new technology or new opportunities may contribute just as much to keep intact the dynamic character of science. And inspiration has often come as much from the planets as from the stars.

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[1] T.S. Kuhn. (1957) The Copernican Revolution. Harvard University Press.

[2] S. Toulmin and J. Goodfield (196 ) The Fabric of the Heavens.

[3] Ibid.

[4] Ibid.

Value of space science

The Dimming of Starlight: The Philosophy of Space Exploration

Ch. 1b

The notion that science and space exploration go hand in hand may seem obvious to a casual observer, but it has been bitterly contested over the years. Many scientists, perhaps the majority of scientists, were opposed to the Apollo program, to put a man on the Moon, on the grounds that it was political showbiz and not science. And just about every important field of space science has been denigrated, at one time or another, in the most prestigious and established quarters of science. Some of those fields still are.[i] And if we pay attention we may still hear rumblings that all that money should go for truly important research. Indeed, a common complaint, particularly in the physical sciences, has been that space science is merely applied science, and thus it would follow that, if we wish to forge changes to our fundamental views of the world, we should concentrate on putting our money and effort into fundamental science, not into space science.

In my reply I will show how every main branch of space science leads to new perspectives of immense value. I will argue in Chapter 4 that several of the main problems that our planet confronts now (e.g., the depletion of the ozone layer and global warming), as well as those it will probably confront in the next few centuries, are far more likely to be solved thanks to space exploration in two ways. The first is that such problems tend to be global problems and space technology is particularly well suited to study the Earth as a global system. The second is that as we explore other worlds we gain a broader and deeper understanding of our own planet.
From comparative planetology we will move on to space physics and astronomy, two fields ripe with the promise of radical changes to our scientific points of view. Such changes will in turn yield an extraordinary new harvest of serendipitous consequences for technology and for our way of life. The reason these two fields are ripe with promise is simple. The Earth’s atmosphere limits drastically the information we receive about the universe because it blocks much of the radiation that comes in our direction. This shielding is, of course, a good thing, for otherwise life could not exist on our planet. But to make even reasonable guesses about the nature of the universe, we need that information. That is why we need telescopes in orbit and eventually on the Moon and other sectors of the solar system. Until the day when space telescopes began to operate, many physicists thought of space physical science as applied science, mere application, that is, of the very successful “standard model” that explained matter in term of its constituting particles and the forces between them.

But, as I discuss in Chapter 5, physicists had been trying to explain a limited universe – a universe based on what we could observe through a few peepholes in the walls that protected us from cosmic dangers. It had already been known for some time, though not widely, that the visible mass in galaxies did not exert enough gravitational force to keep their outer rims of stars from being flung into intergalactic space. Astronomers presumed that eventually the missing mass would be found, but when space telescopes gave us the whole electromagnetic spectrum to look for that mass, we still could not find enough of it. According to some high estimates, up to 90% of the mass needed to account for the behavior of galaxies is undetectable (“dark matter”), apparently unlike the matter explained by the “standard model.”

To make a bad situation worse, in the late 1990s space astronomers discovered that the expansion of the universe was accelerating, even though we should expect that, after the Big Bang, gravity would slow down the rate of expansion. A new form of energy (“dark energy”) is supposed to explain this bewildering state of affairs, once we determine what its properties are.

Fundamental physics, which uses the “standard model” to think about the universe, explains familiar matter and energy. But most of the universe seems to be made up of unfamiliar dark matter and energy, perhaps even upwards of 90% when you combine those two. This means that thanks to space science we found out the extraordinary extent of our ignorance, and that space science is a necessary tool for developing a new physics.

Space exploration is also ripe with promise for biology. This promise is particularly interesting in the case of the astrobiologists’ attempt to search for life in other worlds. For example, when a NASA team announced in 1996 that a Martian meteorite contained organic carbon and structures that looked like fossils of bacteria, meteorite experts adduced that inorganic processes could account for all the substances and structures found in the meteorite. Therefore, these experts claimed, by Occam’s razor, we should reject the (ancient) Martian-life hypothesis (Occam’s razor is a principle that favors the simpler hypothesis; it is named after William of Occam, a medieval philosopher). Other scientists pointed out, in addition, that the presumed fossils were about one hundred times smaller than any known bacteria, too small in fact to be able to function as living organisms. But as we will see in Chapter 6, Occam’s razor would, if anything, favor the Martian-life hypothesis; and, ironically enough, the claim about the minimum size of living things spurred a search that, according to some, yielded many species of extremely small bacteria, nanobacteria, some even smaller than the purported Martian fossils![ii] Space biology proper (doing biological experiments in space) has not yet produced such spectacular and significant discoveries, but, as we will also see in Chapter 6, the main objections against its scientific value are based on misguided distinctions between fundamental and applied science not unlike those advanced some years ago against the space physical sciences. Some of these objections are also based on mistaken assumptions about genetics, and particularly about the relationship between genotype and phenotype.

[i] These points will be discussed in detail in Chapters 3-7. Stephen G. Brush has aptly illustrated the significance of the space sciences to the development of physics, as will be seen particularly in Chapter 5.
[ii] This is a controversial matter, but I will argue in Chapter 6 that this particular controversy is beneficial for biology.

Next Posting: brief summary of the additional controversies about space exploration to be explored in this book: humans vs. machines in exploration; space colonization; terraforming; travel at relativistic speeds; travel faster than light; SETI; space and war.